This invention relates to electric pulse generating methods and apparatus for the ignition systems of internal combustion engines having at least one piston moving within a cylinder and more particularly to such apparatus making it possible to obtain an automatic ignition advance.
An internal combustion engine, in particular for automobiles, includes at least one cylinder in which a piston moves. On the wall of the cylinder are fixed an inlet for a gas mixture consisting of a comburent and a fuel, an ignition system making it possible to obtain the combustion of the two gases and an exhaust manifold for removing the burnt gases. The ignition system generally consists of a spark plug which can produce electric sparks between two electrodes, these sparks achieving the ignition of the combustion gases.
The piston of the motor is driven reciprocatingly or, even rotatingly in certain cases, within a cylinder to compress the combustion gases which, after compression, are burnt by means of the spark produced between the two electrodes of the spark plug. The combustion of the gases makes it possible to drive back the piston. The reciprocating motion of the piston is maintained under the reaction of the combustion of the gases and by the inertia of the moving mass and, in particular, of a crankshaft to which the piston is connected through a connecting rod. By means of a take-off from this crankshaft, it is possible, for example, to drive the wheels of an automotive vehicle.
It is known that, in an internal combustion engine, in order to obtain maximum efficiency, it is necessary for the ignition of the combustion gases to take place at low rotating speeds of the crankshaft, when the combustion gases are under maximum compression, i.e. when the piston is in the so-called "top dead center", that is when it is substantially in the position at which its speed of translation is cancelled and reversed and at which it determines, in the cylinder, the smallest volume. On the other hand, for higher crankshaft rotating speeds, the ignition of the gases must take place before these gases are under maximum compression, i.e. before the piston reaches its top dead center. The higher the engine rotating speed, the earlier must be the ignition of the gases before the piston reaches the top dead center.
The aforesaid conditions determine the adjustment of the ignition advance for an internal combustion engine.
At the present time, most automotive vehicles have a mechanical ignition advance adjustment. There are vehicles on the market in which the ignition advance adjustment is done in a fully electronic manner. Different devices and methods are known for the generation of electric pulses for the ignition systems of internal combustion engines.
None of the presently known electronic devices for ignition advance adjustment gives full satisfaction because they are either too complex or designed only for particular types of internal combustion engines, or, as is often the case, they are too voluminous and costly.
It is an object of the present invention to provide electric pulse generating apparatus for the ignition system of internal combustion engines making it possible to obtain a low-cost automatic ignition advance adjustment of simple design and, especially, of much smaller size than those of the prior art owing to the almost exclusive use of integrated circuits.